Synthesis and use in palladium-catalyzed asymmetric allylic alkylation of new planar chiral chromium complexes of 1,2-disubstituted arenes having pyridine and aryl phosphine groups

Optically active (1,2-disubstituted arene)chromium tricarbonyl complexes 4- 7 having pyridine and aryl phosphorus groups were synthesized from (o-disub stituted benzaldehyde)tricarbonylchromium. These chromium complexes have be en used as chiral ligands in the asymmetric allylic alkylation of rac-1,3-d iphenyl-2-propenyl acetate 8 catalyzed by (eta(3)-allyl)palladium complex. The enantioselectivity increases as the number of electron-withdrawing subs tituents in the aryl phosphine increases. Significant solvent effects on th e enantioselectivity were observed for 4 and 7. By the judicious choice of the planar chiral ligand, high enantioselectivities (90% R, 93% S at 0 degr ees C) were observed. (C) 1999 Elsevier Science Ltd. All rights reserved.